1. Technical Field
This invention relates to gas turbine augmentor fuel manifolds in general, and to gas turbine augmentor fuel manifolds retaining devices in particular.
2. Background Information
Performance aircraft often employ an augmentor immediately downstream of the turbine to produce additional trust. The augmentor typically includes an annular or bar type fuel manifold unit, a bluff body assembly, and a plurality of ignitors. An annular fuel manifold unit, for example, typically includes a plurality of hollow annular manifolds, each having at least one feed tube. During augmentation, an augmentor fuel control supplies fuel to the manifolds through the feed tube(s). When augmentor demand stops, fuel within the manifolds either returns to the augmentor fuel control through the feed tubes, or exits through ports located in the feed tubes. The bluff body assembly, positioned immediately downstream of fuel manifolds, creates quiescent pockets within the core gas path where fuel can be ignited and combustion maintained. The ignitors ignite the fuel mixture within the quiescent pockets.
The core gas path provides a harsh environment for the fuel manifolds. The manifolds are exposed to large, rapid thermal changes that cause thermal expansion and contraction. In addition to the mechanical stresses caused by thermal expansion and contraction, the manifolds are also subject to considerable mechanical loads caused by the core gas acting on the manifolds. Vibrations in the fuel manifolds and/or feed tubes caused by periodic or random mechanical forcing functions can lead to cyclic fatigue.
Hence, what is needed is an augmentor fuel apparatus that tolerates a harsh thermal environment, one that tolerates uniform and non-uniform thermal expansion and contraction, and one that avoids vibration induced fatigue.